A recent National Academy of Sciences (NAS) report says the development of algae-based biofuels poses sustainability concerns. Issues include the large amount of water used for algae cultivation, and the magnitude of nutrients, including nitrogen, phosphorous, CO2, needed. This does not pose a definitive barrier to future production, but innovations are needed to help algae-based biofuels reach their full potential, the report says. For example, to produce 3.15 liters of biofuels, about 3,650 liters of freshwater are...